This invention relates to rollers and pulleys, especially to tension rollers for belt drive or the like, comprised of a hollow body having at least one bottom closed and defining a hub, wherein the roller is held to a machine frame or the like by means of a screw extending through a bore in the bottom of the hub and thread into the machine frame. Such an arrangement further includes a rotating body, such as a pulley wheel, supported by a rolling bearing on the hub.
Rollers for belt drives are known in which the hub for the roller is comprised of a hollow body, the hub being affixed to a machine frame by means of a screw, and wherein a rotatable body such as a pulley wheel is mounted on a rolling bearing supported by the hub. In a known arrangement of this type the head of the screw extends axially beyond the end surface of the hollow body, so that a mounting tool can be easily employed to engage the screw.
This is also the case in another known tension roller, (DE-GM7328570), wherein the hub directly forms the inner bearing ring of the rolling bearing. In this arrangement the hub is detachably affixed to the machine part by means of a screw extending eccentrically through the hub. The belt tension may be adjusted by the provision of an adjusting surface on the hub adapted to be engaged by an adjusting device, such as a key surface, by turning of the hub about the eccentrically mounted screw. The hub is formed of a hollow body which has a guide element on one or both sides having eccentrically displaced bores, so that the hollow body can be rotatably adjusted about the axis of the screw.
Due to the protruding screw heads the width of the known roller arrangement is relatively large, so that such arrangements frequently cannot be employed due to their space requirements. In addition, the danger arises that connecting parts or adjacent machine parts can contact or collide with the protruding parts and thereby may result in objectionable deformation to the device.
The present invention is therefore directed to the provision of a roller, especially a tension roller for belt drive or the like, wherein the width of the roller is relatively small, so that it can be employed in locations of relatively narrow space. In addition, the invention is directed to the provision of an arrangement wherein the touching or colliding of the roller arrangement with adjacent parts, and thereby the possibly resultant deformation, is avoided.
Briefly stated, in accordance with the invention, the above object is achieved by providing a roller arrangement wherein the bottom of the hollow body or bodies defining the hub are setback from the axially outer facing surface by an axially projecting annular rim, the setback being at least as large as the wall thickness of the bottom. As a result on the one hand the screw heads are displaced further inwardly, and on the other hand, the bottom of the hollow body is stiffened. Preferably, in accordance with a further feature of the invention, the bottom of the hollow body is setback from the axially outer facing surface of the hollow body distance about the height of the head of the screw. As a result, the contact surface of the bottom of the hub with the head of the screw is setback sufficiently far that the head does not axially project beyond the hub. As a consequence, the screw may be shorter, and the distance from the holding point of the machine frame is shorter, such that the loading conditions are affected positively. The hollow body can be produced from a cup or can shaped body, by a drawing process so that the hollow body is stiffened by the resulting double fold in the material. In addition the setback contributes to the alignment of the rolling bearing.
In accordance with a further feature of the invention, the inner race of the rolling bearing can be formed directly in the outer surface of the hollow body. Alternatively, however, the inner ring of the rolling bearing, carrying the inner race, may be separate and mounted on the outer surface of the hollow body.
In the latter case it is advantageous to prepare the hollow body from two cylindrical sleeves inserted in the bore of the rolling bearing from opposite sides. These sleeves can contact one another with their facing sides, although it is alternatively possible to provide at least one of the sleeves with a continuous or interrupted radially extending shoulder on its surface which engages the facing surface of the inner ring, for support of the bearing.
In the formation of the hollow body from two sleeves each having one side closed, in accordance a further feature of the invention the bottom of both of the sleeves are setback by axially projecting annular rims from the respective axially outer end surfaces. In the latter case the axially extending annular rims of that sleeve facing the machine frame can be used as a centering surface, cooperating with a centering projection on the machine frame. As a result, the centering or accurate positioning of the roller on the machine frame is obtained without the necessity of widening the roller.
Since both sleeves can be formed with different widths, the distance between the central plane of the roller to the machine frame can be varied, by reversing the mounting position and the roller.
In accordance with a still further feature of the invention, a ring or the like of vibration damping material may be mounted in the hollow space between the projecting annular rim and bottom of the sleeve directed toward the machine frame, and the machine frame itself. This feature results in the damping of the vibrations between the roller and the machine frame.